class Solution {
    public boolean lemonadeChange(int[] bills) {
        int five = 0;
        int ten = 0;
        for(int bill : bills){
            if(bill==5){
                five++;
            }else if(bill==10){
                if(five==0){
                    return false;
                }else{
                    five --;
                    ten++;
                }
            }else{
                // 20 
                if(five>0&&ten>0){
                    five--;;
                    ten--;
                }else if (five>=3){
                    five-=3;
                }else {
                    return false;
                }
            }
        }
        return true;
    }
}